This invention relates to plasma tubes and to methods for their manufacture and more particularly to a reliable, low cost plasma tube particularly suitable for use in manufacturing helium-neon electron-excited gas lasers.
In the past it has been common to build envelopes and associated components for helium-neon gas lasers of a borosilicate glass, such as Corning brand Pyrex 7740 or 7052 glass, widely used for laboratory glassware. Such glass has good thermal properties in that it is resistant to thermal shock, has good thermal conductivity, and also has a low coefficient of thermal expansion. However, it is also known that there are few, if any, metals to which borosilicate glasses can be joined without the use of some sort of graded seal or Housekeeper seal. Accordingly, envelopes for gas lasers have generally required the use of expensive glass forming or molding techniques in order to establish the envelope configuration. The required metallic conductor parts have generally consisted of small-wire tungsten seals through a graded seal in 7740 or Kovar metal seals in 7052 borosilicate glass because of the limitations of glass/metal seal technology. Accordingly, prior tubes have usually been made of all glass structural parts, including seals, tip-offs, and the like, through which special non-structural conductive elements must pass in order to establish an electrical discharge. There is, therefore, a need for an improved gas envelope structure plasma tube and method of manufacture which will overcome the foregoing limitations.